Formation and use of a video train including echo signals, amplitude modulated range m arks, and cursor pulses, all bracketed by time-spaced control pulses



I Sept. 23, 1958 H. T. HAYES 2,853,

FORMATION AND USE OF A VIDEO TRAIN INCLUDING ECHO SIGNALS, AMPLITUDE MODULATED RANGE MARKS, AND CURSOR PULSES, ALL

BRACKETED BY TIME-SPACED CONTROL PULSES 21, 1951 8 Sheets-Sheet 1 Filed Sept l l L.-

NA w v m F in m mw m V ILM 5 HI 5 m m m 4 6 1m 4T m 4 H. T. HAYES I 2,853,763 FORMATION AND USE OF A VIDEO TRAIN mcwnmc ECHO SIGNALS,

Sept. 23, 1958 AMPLITUDE MODULATED RANGE MARKS, AND CURSOR PULSES, ALL

B5RACKETED BY TIME-SPACEID CONTROL PULSES .1 1

8 Sheets-Sheet 2 Filed Sept. 21

INVENTOR HARRY 7. HAYES A W J V w SIGNALS, ALL

8 Sheets-Sheet 3 ma mas:

, AND CURSOR PULSES H. T. HAYES BRACKETED BY TIME-SPACED CONTROL PULSES 21, 1951 FORMATION AND USE OF A VIDEO TRAIN INCLUDING ECHO AMPLITUDE MODULATED RANGE MARKS AWNWS 353m H mm Sept. 23, 1958 Filed Sept a sis f/v VE/V TOR. HARRY 7: H6765 H. T. VIDEO Sept. 23, 1958 HAYES 2,853,703

SIGNALS, ES, ALL

8 Sheets-Sheet 4 FORMATION AND USE OF A TRAIN INCLUDING ECHO AMPLITUDE MODULATED RANGE MARKS, AND CURSOR PULS BRACKETED BY TIME-SPACED CONTROL PULSES Filed Sept. 21

2,853,703 TRAIN INCLUDING ECHO SIGNALS, MARKS, AND CURSOR PULSE Sept. 23, 1958 H. T. HAYES FORMATION AND USE OF A VIDEO AMPLITUDE MODULATED RANGE S ALL BRACKETED BY'TIME-SPACED CONTROL PULSES Filed Sept. 21, 1951 8 Sheets-Sheet 5 ll] 55% i Mk3 \QNQ kw xxx Mamet v 4 [N v/v TOR HARRY 7. HAYES BY 4 a firing/W345 H. T. HAY-ES Sept; 23, 1958 FORMATION AND USE OF A VIDEO TRAIN INCLUDING ECHO SIGNALS, AMPLITUDE MODULATED RANGE MARKS, AND CURSOR PULSES, ALL

BRACKETED BY TIME-SPACE!) CONTROL PULSES 8 Sheets-Sheet 6 Filed Sept. 21, 1951 Sept. 23, 1958 H. T. HAYES 2,853,703

FORMATION AND USE OF A VIDEO TRAIN INCLUDING ECHO SIGNALS, AMPLITUDE MODULATED RANGE MARKS, AND CURSOR PULSES, ALL

BRACKETED BY TIME-SPACED CONTROL PULSES Filed Sept. 21, 1951 8 Sheets-Sheet 7 1,0 m. DEMYINI "C 'Teza.

c/m/wva Carer/aw C/MAWI:

I [NVE/VTOR HARE Y Z HAYES prraex/a s Sept. 23, 1958 SIGNALS, AND CURSOR PULSES, ALL ME-SPACED CONTROL PULSES HQT. HAYES 2,853,703 FORMATION AND USE OF A VIDEO TRAIN mcwnmc ECHO AMPLITUDE MODULATED RANGE MARKS BRACKETED BY TI Filed Sept. 21.1951

8 Sheets-Sheet 8 m mov+ cm. 0

NhmQbk N 3 W H 0 NT 7 5 Wm Y hu M Y B Application 'september 21, 1951, Serial 190;247:738

.llClaims. (Cl. v343-41) Th -nresea 1in en ion.- rela s t imp ved ech q e and means, 1, particularly vuseful in cathode ray tubej indica rs of the type such as found in theso-called precis on e tio -pf 'G oun co app c radar-aircraft landingsystems, but is of course not necessarily limited to use in such equipment. in general the present application is directed to specific features of the system described and claimed in my co-pending application in whichjl am listed with Landee, et al.,'as one of the joi ntlinventors,,such co-pending application having "Serial 'No."247,'616, filed on even date herewith, and assignedjo the present ,assignee and ,having matured as 'ln, gener2i l, ,the present invention relates'to apparatus and techniguesformixing or placing various components on the composite videoltrain used in the system described 'in ,;the aforementioned copending application; more specifically,-the present inventionrelates to improved techniques and apparatus for mixing various components "on-a composite 'video train with such composite video jtrain includinga pair got time spaced so-called'C and L "triggers; between which is bracketed variousvoltages for -thereto.

" The features 1 of the present invention which are-be- "lieved to be novel are set forth-with particularity in the appended claims. This invention itself, both as to its Patented Sept. 23, 1958 'ice Figure 6 showsthe cyclical variation of azimuth and elevation beam angle voltages in relationship to the related position of the corresponding radiated azimuth and elevation antenna beams, such variation being preferably linear and being obtained -in the corresponding beam angle-coupling unitsshown in Figure 2 for ;use: in developing V=follower informationin accordance with features of the present invention;

Figure 7 shows in more simplifiedforni=apparatusindicated in block'form in Figure .3.;

Figure 8 shows inimore detailed formthespecific circuitry of elements indicated in block form in Figures "3. and 7;

Y Figure19 shows .a centering-circuit for cyclically-Nat? ing the origin of the radial sweeps, namely the points '0 and O irr Figure 1;

Figure 10 is a schematic representation. showing-in more detailed form some of the apparatus indie-211266 in block form in Figure 4;

-;Figure 11 shows the time relationship between-various triggers, range marks, cursor pulses and echo ,signals developed by theapparatus described herein;

:Figure 12 shows in somewhat, more detailed form the time relationship -,of other triggers, range marks, p ulse s, gates and sweeps ,generatedbythe apparatus shown in .the previous figures, it being noted that such: time relationshipsareshown on ;a logarithmic-scale and as shown .ar uuse ulin p o n 'l a thm ype o disp ay of stheieharac er d ibe and cla me in th pcnd ng p ten applic i n of vH m vG- I s e an -M in Shuler, Serial No. [175,168, filed July 21, 195( now PatentjNo. 2,737,-6 54,-issue d March 6, 19 5 6, and asre n d t thas m ass ug it is unde s o ;that otherwise the time relationships are such as'to-produceithe linear type of display shown in;Figure 1,;

Figure '13 illustrates the sequential development of the azimuthand elevation unblanking voltages in relationship to the-relay, gating voltage as developed by;t he-apparatus shown in Figure 2;

' description in the aforementioned copending patent 'application,--which is incorporated herein by this reference organization and manner-of operation," together with fur- ,ther objects and advantages thereof, may be best-understood 'by -reference to'the-followingdescription taken in 'connection-withthe accompanying drawings in-whieh:

Figure 1,shows both anazimuth versus range and an elevation versuszrangei i. e., a so-called Az-Eldisplay on the viewing surface of-a cathode ray tube; the range marke -spaced at equal time intervals, being intensity modulated-inaccordance with features of thepresent-fin- "vention for conveying V-follower information;

FigureZ shows in schematic form antennabeam scan- -ning-' apparatus -and--related switches-and other apparatus -controlled thereby;

'Figure 3 'is a block diagram of apparatus intended to be connected to correspondingly designated terminals 1 inF-igure 1;

,Figure 4 showsin block diagram form certain -.apparatus. connected to correspondingly desi nated termi- -.na1 ;i.n Fig re Figure- 5; servesto represent the; cyelical variation of azimuthxandelevation beam ,angle scanning; periods, I operation of ,the relays -,and corresponding times in'whioh-the cathode ray tube -is being usedito develop either the elevation or azimuth ,-display, as the casemay be, on

a time sharing basis;

Figure 14 shows a voltage regulating circuibfor-eompensating for loadchanges and serves essentially to-main- 'tain a voltage of volts derived.from a 300 .volt .source, the regulating circuit functioningto produce compensatory effects for load changes;

,Figure 15 illustrates the time sequenceof-yarious.volt- .ages and theperiod of, conduction of two tub.es in the ,apparatus illustratedin the previous figures.

In ;ge neral,:,the system described herein servesto producewisible indications in cathode ray tube displays which .are shown in Figure 1. ln Figure 1 it is observed that there are actually two ,displays,;an upper elevation displayand a lowerazimuth display. Both of these displays are produced electronically usinga single electron gun structure operating on a time sharing basis ,The present invention'relates particularly to ,the mannerin which the composite video is applied toa cathode-beam intensity control electrode, i. e., the ,control grid or the eathode, for purpose of obtaining visible indications in the displays.

This composite video includes, as shown inFigure ll: (1) ,Ihe returning radar echo signals; (2) therange marks which areessentially .alignedvertical lines in the azimuth and elevationdisplays; 3) intelligence inthe form of amplitude modulation on the range marks ,for developing so-called V-follower lines in both azimuth and elevation displays, the V-follower lines in theazimuth display in Figure 1 serving .to indicate the position in azimuth of the elevation antenna, and conversely the V-follower. lines in the. elevation display serving to indicate the position in elevationof the a-zimuthantennmand (4) cursor pulses for producing electronically the predetermined sate glide 3. path course line in the elevation display and the corresponding runway course line in the azimuth display. It is noted that this aforementioned train of information, i. e., composite video train, in the form of signals and pulses, is bracketed between so-called C and L triggers.

Briefly, as described in greater detail hereinafter, the C trigger is used to indicate the start of a gating voltage, and the L trigger terminates such gating voltage. Such gating voltage is applied to an intensity control electrode, i. e., the grid of the cathode tube, so as to condition or allow the cathode tube to produce visible indications in accordance with the various voltages which comprise the composite video. In other words, the components of the composite video are insufiicient in themselves to produce visible indications on the cathode ray tube viewing surface, but require the presence of such gating voltage on the first anode of the cathode tube for producing visible indications.

It is observed that the composite video signals shown in Figure 11 do not, as such, include a designation of the V-follower voltages for producing the aforementioned V- follower lines, since such V-follower voltages are used in the present system to modulate, i. e., either to intensify or alternatively to de-intensify range marks.

It is evident that other periodically appearing voltages may be included in the composite video which is in the form of a train of signals having a length or time duration measured by the spacing between the C and L trigg rs, and therefore the present invention in its application is not limited specifically to voltages for producing the specific information described herein, but finds application in other systems wherein the compo-site video may include other intelligence denoting voltages or pulses. One of the important features of the present application is that such com osite video train is applied and is effective to produce visible indications only during the duration of an established gating voltage. This gating voltage may be of constant duration for each cathode beam sweep, or may, as described herein, be of varying duration for purposes of obtaining tailored azimuth and elevation displays whereby most efficient use may be made of the cathode ray tube viewing surface.

While Figure 11 shows the composite video train in relationshin to the C and L triggers, their relationship to other pulses or voltages in the complete radar sys em is shown in Figure 12. In Figure 12 the so-called Al trigger is the system trigger and is the one generated in synchronizer 31 (Figure 2). The A1 trigger causes operation of the transmitter 34 and resulting antenna beam from the azimuth antenna or elevation antenna, as the case may be, depending upon the particular position of the radio fre quency switch 36. The C trigger appears after the A1 trigger with a very small time delay. The C trigger is applied to the cathode beam sweep generating means for purposes of initiating a cathode beam sweep and serves to initiate the D trigger, as indicated in Figure 4. For remote control purposes, the amplitude of the C trigger is 12 volts when the azimuth displays is being produced, and is volts when the elevation display is being produced.

While the series of range marks are initiated by the A1 trigger, they are adjustable along the time base axis as a unit, so that the first range mark occurs after the D trigger, and such first range mark corresponds to the aircraft touchdown point in either the azimuth or elevation display, as the case may be. The range mark generator for accomplishing such adjustability may be of the type described and claimed in the copending application of Pete Korelich, Serial No. 211,513, filed February 17, 1951, now Patent No. 2,698,401, issued December 28, 1954, and assigned to the same assignee as the present invention.

The L trigger is initiated by the C trigger but occurs with variable time delay after the C trigger, as indicated by the arrow on the L trigger in Figure 12, for purposes runway course lines, 1

of limiting, clipping or tailoring the Az-El display. The L trigger is produced in the map generator (Figure 7), the circuitry and techniques involved in the same being shown and claimed in the copending application of Raymond B. Tasker, et a1, Serial No. 222,512, filed April 23, .1951, and assigned to the same assignee as the present invention. As alluded to before, the L trigger determines when the intensity gating voltage applied to the control grid is stopped. The amplitude of the L trigger is the same as the amplitude of the C trigger during the azimuth and elevation presentations.

While for purposes of describing certain aspects of the present invention, the C and L triggers may have the same amplitude during the presentations of both the elevation and azimuth displays, they are shown as being modulated in amplitude to indicate the manner in which the present system described herein is adapted for the transmission of the video information to a remote location in accordance with an alternative arrangement described in my above mentioned Patent No. 2,796,603. When the present system is connected for remote operation, information as to the angular position of the radiated antenna beam is conveyed to such remote location in the form of a pair of triggers, i. e., a so-callcd reference trigger and a data trigger, and such reference and data triggers shown in Figure 11 are included herein for reference purposes and are utilized in the apparatus described in connection with the alternative arrangement shown in said Patent No. 2,796,603.

The apparatus for producing the composite video trai of signals shown in Figure 11 includes means for generating the various intelligence denoting voltages and mixing the same so that they may be applied jointly between the C and L triggers to the cathode of the cathode ray tube. A portion of this apparatus is shown generally in block diagram in Figure7.

In Figure 7 the composite video train appears in the so-called composite video line drivers which have four output terminals. Terminals labeled No. 1 and No. 2 are used for remoting purposes. The terminal No. 4, as shown in Figure 4, is coupled to the cathode 11 of the cathode ray tube 12 through a delay line 13 and amplifiers 14, 15, 16, while the output appearing on terminal No. 3 is applied to a network or gate channel indicated also in Figure 4 and shown in more detail in Figure 10 for separating the C and L triggers from the composite video train, and utilizing the same to form a gating voltage which is instituted by the C trigger and terminated by the L trigger, such gating voltage being applied to the grid 17 of the tube for purposes mentioned previously.

The range marks are produced in the range mark generator 18 in Figure 7, and are initiated by the A1 triggers, i. e., the radar system trigger. The output of the range mark generator 18, however, is modulated, i. e., either intensified or de-intensified, in accordance with voltages developed in the servo indication mixer and amplifier stage 19. Azimuth servo data and elevation servo data applied respectively to the elevation picture channel 20 and azimuth picture channel 21 are alternately supplied on a time sharing basis to such mixer and amplifier stage for producing the aforementioned modulation. Elevation and azimuth angle voltages are applied to the elevation and azimuth picture channels 20, 21, respectively, for developing the modulation component, so that such modulation component varies in accordance with the angular position of the radiated azimuth or elevation antenna beam, as the case may be, in the manner described later. The range marks thus modulated are applied to the range mark cursor and servo mixer 22, to which is applied cursor pulses developed in the map generator 23. It is noted that these cursor pulses are used to produce the glidepath and .-;plied.= -with= :eithBI; azimuth -.-or' elevationbeam angle voltagen as.zthecase' may ;:be,:;on..a;time;sharing basis. The .eoutputsofsthe'zQzand:L trig-ger generator stage 3% is ap- ;-=pliedi.to the ,composite-zvideo tmixer,. 25,- .and h outp of theccomposite video mixer iis; applied "10 thecqntvposite T'Iine driveristage 10.

:More specifically,-the apparatus: described herein-ser es .ato .produce the velevation display 32 and;;a;zimuth;display :53 '-.-in:=Figure' 1==with the predetermined af 'sl path srepresented xbygthe. line ,AB in the: elevation display 132,

.rproducedelectronicallygas-a series of dashes, and to cor- ;respondingly.tproduce electronically the runway -lir 1e in :zthe azimuth:display 33;repres ented by the line CD. This sis-for; the general purpose; of; allowing an observer ,to

track the course of an aircraft'appearing as the dots 158,159 1001,11 6 elevation; an azi u displays, t p atively, -;-wi-th reference-- to su h e cor e ponding dine A and LCD.

It is noted that-gthesedisplays 32,33 areproduced by aradialseathod rray heath swe p Originating :frem t wadjustedielectr ealrente .01, ze the cat eam fdeflectingisystem. JIhe seriespf-vertically aligned lines -i40, 5 4 .3, 44tfi 1 i n i d pl y 3 33 represent 1. rang ;.1 ne 'e-,. h il t u e pe t of con d s- ;:;tar1 e:;t.nem it eieente s- Q1 an '..0z,:a 1the ase m y be- ..Ihe-rang li r-4 passe rt r th a a e e ;l ow pQinLA-enth e a on .di p ey n of course jthIQllgh-jthfi small rectangular ,tab .46 which may be placed on the, face ofgthe cathode ray tube to indicate the;position of;the aircraftlanding strip in the. azimuth display. :Ihe lineAll-in displays 32 and 33 thus reprei-sents z ero distance ,from touchdown. The .lines .41, .42,

43,:44 and 45-,represent, respectively, distances twomiles, fgun miles six ,rniles, eightmiles and ten miles-from the corresponding touchdown point in the azimuth and elevation displays 33, 32.

l Wi1 be ;0bserved that the elevation display,32. and

zimuth display 33;.;are irregular in shape, and such u i ie -i th vdisp ay a ep ed ce by p te im- ..itir 1 g..,or.,C. .iPRiI gs0, as toallow more efficient useof the sliewing surface of the tube and toallow 'the most important portions-of the displays 32, -33 to lie closer to each other. Forpurposes of reference, the elevation ;,disp lay comprises the areadefined by .0 F,.G, H, I, K,

0 ,$imilarly, ,or,,purposes of reference, the azimuth display 33 is,confined.in the area defined by Q L, M, -N, 1 0 The pair of radially extending lines 50, 51

;in' t l 1e elevation ,display are well known so-called ;V- deflowerd ine nan lwh l .th y d no pp as s n either display, yaredefinejd by discontinuities inthe-range marks. rSirnilarly, 1the:-pair,,of radially extending V-fol- -'.lower lines '52 and '53 lin ithe azimuth display 33 indiroates thearea scanned by the. elevation antenna, and are-likewise defined-by obliterating selected portions --o f=- the range marks, .i. e., the-range marks :are modulated in accordance with -the V-follower information to produce discontinuities in the range marks to thereby efiectively'de'fine sucht v follower lines.

The apparatusxfor producing "the "displays .32 and 33 ,:is'zfirst'.rdescribed inconnection' with Figures 2, ,3 and 4 which :have. correspondingly :designated s, terminalsvinter- 6 connected to produce -a: -system zforsproducing the l display shown tin-Figure 1, locally;

Pattern producing means ;In Figure 2 the synchronizer T31 serves towgeherate timing Pulses :which are used to time the operation gQf pulses applied to thettransmitter 34 to initiate its soperation. The transmitter stage 34,=pu lsed .at a constant repetition rate of, for example, 2 ;00O; puls es per second,

;.co1 1 sis ts of, for example, a magnetron oscillator W.i,th .-a

characteristic frequency ,of about l0,000 megacyc le s. The output of this transmitter .stage 3.4 is transferred to either thefelevation (El) antenna -54-ofi,azimuth (Az;) an n :55, d pend upon t p s io of t :r e or driven interrupter or radio frequency switch -,-36. The transmit-receive (T- R) switch 56 prevents;;power.;from the transmitterzfifiijrom being applied directlylO Ithe I receiver 57. This transmit-receive switch,35,.-as. is well known in the arteallows low .intensityssignals such as a trarnof resulting echo signals receivedon the antennas 54, 5 5 to be t ransferred.to the inputterminals ofthe receiver. 57. p

This diversion of energy from the transmitter 34 ,to

the-antennas 54, 55, accomplished by operation ;of switch 36, occurs at a ,rate of approximately- 2 per second, so

that inefiect the .combinedantennasobtain 4"looks per "second of th e,space scanned. The ,resulting antenna ;hea msare ,caused to moveangularly, i. e, to scanupon -;rota tionof the-shaft 58. The -switch 36 ,is rotatedtwice ;-per. second, and whileenergy is being-transmitted t0'.- 0ne 'e the a ten as ty h e u ti g. le tr magn t ;beam projected i nto-space is caused -;to scan suchsspace, The means wherebysuch scanning mouement of theprojected v rl etr ntn s et y am s ob a n mayb lot th type de c be in the p d e .epp iea ienef Karl. A- All a h, .Seri l.-Ne- 910, ,file epte ber '8, l'9i48,;tfe

i yp B e i on. t nn i Stru ur n w Paten No. 2,596,l13,';issued- May 13, 19 52,. which depends for its operation -on the use of a variable waveguide gtype e -ant nn h s pa cular m a s p e, orms Qn part ofthe present -invention;and, so far as theaspects of the present,;invention ,-are concerned, the antenna scanning beam maybe produced by moving-theentire antenua;through ,a relatively small .arc ofua ,cinele- Actually, in fact, the azimuth;antenna beam tmay scan fi r st in one direction and then in the ,othenwaitingyafter each scan-while lthe elevationgbeam c0mPletes,. a scan ,in elevation.

While ,in any position-during the part of the cyc le in which ,the switch 36 allows the flow of energy to :the elevation, antenna 54, ;the elevation antenna :beam is, electrically scanned i i-elevation. The angular; position of the elevation antenna beam is-measured by means of,a variable capacitor.5 9 onplateof whichis attached ,to the beam scanner. of elevation antenna 54 'and varied ,in accordance ;th,erewith,,s,u ;h capacitor 59 comprising one part of a capacitative potentiometen. contained in the angle coupling unit 60, which may beof the type described ,and claimedin t he,.c,op ending patent applicationof George B. .Crane, .Serial No. 212,114, filedFebruary 21, r1951,

-now Patent No. 2,650,358, issued August 25, .9.53.

The angle coupling unit 60 thus used with angle capacitor 5? is usefulin .developing the .elevationflbeam angle voltage represented. as .61 inFigure 6. i

Similarly, the angle, in azimuth ofthe, azimuth antenna beam is measured by the angle capacitor.62 in az in 1 1th angle coupling unit 63, operating synchronously with the scanner of the azimuth antenna SS. Such variation in azimuth angle voltage as a' function of the particular angular position of the antenna beam; is represented by the cyclically -varying voltage 63 shown in Figure '6. It is observed that these voltage variations 61 and- 63 have: portions thereof'shown in heavy-lines anditzis these portions which; are: used :to effect control: operations, and

whichiareselectedmyrmeans rneutiQnedlater.

also. connected to the deflection coils.

.,stages.100and 101, for purposes of modulation, receive much smaller degree and in a diiferent manner, for purpsesof orientation as described'later.

"Thus, the amplitude of the currents supplied to coil 91 ;is-automatically varied in accordance with antenna beam angle voltage, so that the angle which any particular cathode ray beam makes, corresponds, onanexpanded scale, to the antenna beam angle.

The tube 12 is rendered fully operative for producing visible indications only when a suitable intensifying voitage is applied to its grid 17, bringing the tube approximately. to cut-off condition. A relatively small additional video signal applied to the cathode 11then strengthens the cathode beam, making it momentarily visible-on the scre en as a dot, the positionof which isdetermined by the currents flowing at that particular moment in the set ofdeflection coils 90, 91.

For purposes of developing the aforementioned suitable deflecting currents in the cathode ray deflection coils 90 and 91, the sweep generating circuit shown in Figure 4 .is supplied with C triggers which. appear in timed relationship and as a result of Al triggers developed in synchronizer 31 (Figure'Z). areapplied in Figure 4 to the delaymultivibrator and vblocking oscillator stage 98, the output .of which is fed Such C triggers to the sweep generating multivibrator stage 99. A negative gating voltageisgenerated in the stage'99 and fed t o ,the expansion ,and time base modulator stages 100 and101, .respectively, and from them in modulated ;=form through expansion and time base amplifiers 102 ,,-and ,103. .The output of amplifiers 102 and 103, in the form of essentially trapezoidal waves of appropriate am- ;plitude, are applied to the expansion deflectioncoil 91 and lithe time base deflection coil 90, respectively, causing cur- .rent pulses of .linearsawtooth form in thecoils. Expan- .sion1 and:time base centering circuits 105 and 106 are antenna beamangle voltages via switches m and in, respectively, .of relay K1101.

With the relay unactuated (as shown) the elevation tbeamangle voltage appearing on thevpotentiometer resistance108 is applied through switch in to the expansion modulator 100; and through potentiometer resistance 109 and,;inverter 110 and switch n to ,the time base modu- -l;ator 1. After completion of the elevation scan, relay K1 101 is actuated-by switch 69 (Figure 2) breaking the :elevation beam angle voltage connections just described, :and connecting the azimuth beam angle voltage through potentiometer 111 and switch in to the expansion modulator 100; and through potentiometer 112, inverter 113 rand switch it to the time base modulator 101.

. Thus, the degree of modulation of sweep current, and hence the degree'of angle expansion of the display, may

be separately regulated for the azimuth display by ad- ..justment ofthe potentiometer 111, and for the elevation .idisplayby. adjustmentof potentiometer 108; and thede- ;dividually capable of two separate adjustments, one effective when relay K1102 'is actuated (azimuth display) and one when the relay is unactuated (elevation display) to determine the positions of the points 0 and 0 respectively inFigure 1. Thus, the origins ofazimuth and The modulator elevationdisplaysare separately adjustable, "the centering circuits automatically responding to one or other set-ofadjustments according to the energized condition of relay K1102. A schematic diagram showinga centering-circuit forthis purpose is shown in Figure 9.

The deflection coil 91 in Figure 9 is connected .between a 700-volt positive supply and twoparallel circuits,

one leading to :ground through tube V1116, which is the finalstage of expansion amplifier 102, and the other :leading through choke coil L1101 and centering tube V1117 to a IGGG-volt positive supply. The first of these two circuits feeds to deflection coil 91, the periodically varying sweep producing component while the second cir- .cuit' provides a relatively constant but adjustable centerins current component. The cathode resistor of centering tube V1117 is made up of two paralled connected I otentiometers R1158 and R1159, the movable contacts of which are connected respectively to the normally closed and normally open contacts of switch in of relay K1102. A switch arm is connected through grid resistor R'7-to the tube grid. Thegrid bias, and hence the centering current through the tube and through the coil =91 thus depends upon the position of relay switch .m

and is determined by the setting of potentiometerR1159 when relay 14.1102 isactuated (azimuth display) and-by the setting of potentiometer R1158 when the relay is not actuated (elevation display). The two displays arethere- -fore separately adjustable as their vertical position (expansion component) on the indicator tube ,by means of the two potentiometers.

Time base deflection coil'90 is provided with centering circuitrywhich is identical to that in Figure v9 and --functions in a like manner, controlled by switch n of re- --layK'1=102. In fact, by appropriate changes of the nu- -merals and lettering, Figure 9 may be considered to illustratethe time base centering circuit. Thepotentiometers'then provide separate adjustments of the elevation and azimuth displays with respect to their horizontal po- Formation of composite video train The manner in which the composite video train is produced is'alluded to above with reference to the previous description of Figure 7. For the following detailed explanation reference is made at this timenot only to Figure 7 but also to Figures 3 and 8, as well as Figure 2 which discloses means for developing V-follower information, i. e., azimuth and elevation servo data. Itis noted that Figure 3 is a block diagram, while Figure 8 shows the same apparatus as indicated in block diagram in Figure 3, and that the various tubes, delay lines and relays in Figures 3 and 8 have the same characteristic reference numerals; for example, the block in Figure 3 havingthe label V9301A is applicable to the same designated tube in Figure 8. The range mark generator18 serves to generate range marks in timed relationship with the Al triggers applied thereto, and this range mark generator may be of the character described and claimed in the aforementioned copending application of Korelich.

The amplitude of the range marks is either increased or decreased, i. e., modiulated, in accordance with the position of the servo modulation switch 5-9301 in Figures 3 and 8. By this means discontinuities are produced in the range marks to thereby efi'ectively establish the v-follower lines 50, 51, 52 and 53 (Figure 1) in the displays. These lines, of course, are not visible as such in the manner indicated in Figure 1, but-such V-follower 11 lines are shown in Figure 1 for more clearly illustrating certain operational features.

The V-follower information for modulating the range marks is developed in conventional manner, as for example, by the manner described and claimed in U. S. Letters Patent 2,483,644, Kelsey et al., patented October 4, 1949, a portion of which apparatus is shown in Figure 2. In Figure 2 the azimuth and elevation servo data is developed on the leads designated Az Servo Data No. 1, Az Servo Data No. 2, El Servo Data No. 1 and El Servo Data No. 2, such leads terminating at terminals ill-.51, 113, 121 and 12.0, respectively.

Referring now to the schematic diagram in Figure 2, the V-follower voltages for use in the elevation display are obtained from two linearly wound rotary arm potentiometers 1'31, 132, whose arms are adjustably linked together as by the common shaft 137, and are linked to the antenna beam scanning mechanism as indicated schematically at 138, which controls the azimuth adjustment of the elevation antenna 54. The latter linkage, which may be of any suitable type, mechanical or otherwise, is indicated in Figure 2 by a dashed line 137A. Similar linkage between the elevation antenna 5'4 and the mechanism 133 is indicated by the dashed line 1378. The potentiometer strips 131 and 132 are connected in parallel as shown between a positive and a negative terminal of a voltage source and have the variable resistances 133, 134 and R35, 136 in series with them, by which the exact voltage range of each potentiometer may readily be controlled.

For each position of the azimuth adjustment of the elevation antenna, the V-follower voltages taken off the movable contacts of the potentiometer have definite values, the difference between them remaining constant. Each V-follower voltage determines directly the angle on the azimuth display of the corresponding ll-follower data. Thus, the constant difference between the two V-follower voltages determines the fixed angle between the V-follower lines d9, 51 on the indicator tube in Figure 1. As the elevation antenna is rotated to vary its azimuthal position, the entire V rotates correspondingly as a unit about its vortex or origin 0 on the screen. The angle between the V-follo-wer lines 56, 51 and the relationship of each line to the azimuth angle of the elevation antenna may readily be adjusted, for example, by loosening set screws 231A and 132A, securing the potentiometer arms to shaft 137, rotating the arms through the required angle, and again tightening the set screws. Or the same adjustment may be accomplished by shifting the potentiometer tap to higher or lower potentials by manipulation of variable resistances 133, 134 and 135, 136. It is assumed, for the present description, that the arms are so adjusted that the take-off voltage of the potentiometer 1 31 is more positive than that of 132.

The V-follower voltages, obtained as just described, at the movable contacts of potentiometers 131i and 132 are compared by means of the circuitry in Figure 2, with the azimuth angle coupling voltage applied to the two tubes V-93 l6A and V-93ll6B (Figures 3 and 8). As the latter periodically becomes less positive during a given scanning cycle of the azimuth antenna, the relationship between the angle coupling voltage and first one and then the other of the r -follower voltages passes through a particular condition, as will be described, and causes generation of voltages which are used to modulate, i. e., either intensify or deintensify the range marks, as the case may be. More specifically, the two V-follower voltages are applied by leads 139A and 1398, respectively, to the grids of both sections of the cathode follower coupling tube Vi, thus controlling the currents through these two sections and the voltage drops in their cathode resistors 140 and Potentials of the two cathodes of tube V1 are thus determined and are used to control the circuitry shown in Figures 3 and 8.

While Figure 2 describes in detail only the arrangement for developing the elevation servo data, it is evident that the same apparatus may be duplicated and used for purposes of developing the azimuth servo data in the same manner. The azimuth servo actuator for that purpose has the reference numeral 143 (corresponding to servo actuator 13B), and the corresponding azimuth servo data circuitry has the reference numeral 144 (corresponding to the circuit including potentiometer 131, 132).

The servo data modulation circuit shown in Figures 3 and 8 makes it possible to show the beam angle position of the azimuth antenna, in elevation, on the elevation portion of the display, and to show the beam angle position of the elevation antenna, in azimuth, on the azimuth portion of the display. This information is displayed by the intensification or deintensification (at the operators option) of the range marks over the scanning area of the particular portion of the display sector affected. For this purpose, servo data No. l and No. 2, when properly adjusted, vary over the same voltage range as the angle voltage (SO-volts) but are displaced in absolute value by a few volts when adjusted for proper display information (for example, 5-55 instead of 252). Voltage differences between the two leads No. 1 and No. 2, either azimuth or elevation, as the case may be, remain fixed as the corresponding antenna is servoed. Servo data No. l is adjusted to have a lower potential than servo data No. 2, and both values increase, as mentioned previously, as the servo angle of the antenna increases in a direction corresponding to the increase in angle voltage. For example, as the elevation antenna scans upwardly, elevation angle voltage from the elevation angle voltage generator increases; as the azimuth antenna is servoed upwardly, both azimuth servo data voltages increase.

The azimuth servo data lead No. 1 is coupled to the grid of tube V-9301A. This tube is the first half of a differential amplifier, and the current drawn by its cathode places the commonly coupled cathode of the second half of V-93tl2A at a level approximately two volts higher than the existing potential of servo data No. 1 lead. By this means V-93tl2A is held at the cut-off point until the value of the elevation angle voltage applied to its grid reaches a level close to the voltage present on the first grid (this level being the "cut-otf" value for the tube) at which point the tube conducts. The elevation angle voltage increases in a positive direction as scanning action takes place from minus one degree upwardly, and decreases when the scanning direction is reversed; the limits of angle voltage amplitude are established to be plus two volts to plus fifty-two volts. The resultant wave form at the anode of tube V-93tl2A is a negative gate which starts at the instant the tube conducts (the two voltages, azimuth servo data voltage No. 1 and elevation angle voltage, are then approximately equal) and continues until the particular scan period is completed. The action of differential amplifier No. 2 is similar to that described for previously described amplifier No. 1. Servo data No. 2 applied to terminal 118 (Figure 8) is applied to the grid of tube V- 9301B, causing the tube to conduct. The current drawn through the cathode of tube V-9301B places the commonly coupled cathode of tube V-9302B at a potential slightly higher than the servo data voltage. The action in this case is identical to the action described for differential amplifier No. 1 with the tube remaining below the point of conduction until the elevation antenna angle voltage applied to the grid of tube V-9302B approaches the cathode potential and forms a gate on the anode of tion the action is similar, but the order of appearance of the two gates is reversed. The output of differential amplifier No. 1 is applied to the first half of differential amplifier N0. 3, tube V-93tl3A, which is normally conducting at saturation. The appearance of the negative gate lowers servo data No. 2 leads; the starting point is determined by 'thetime at which the elevation angle voltage approximately equals the potential of the azimuth servo data -No. 1 lead, and the terminating point is determined by the timeat which the elevation angle voltage approximately equals the potential of the servo data No. 2 lead.

The elevation servo data leads No. 1 and No. 2 are connected in similar manner to the circuitry which includes the tubes V-9306A and B, V-9307A and B, -V-'9305A-and'B and V'9304B for accomplishing the same type of result in the azimuth display. Thus, gates are formed at the anode of tube V-9305A as a result of modulation of the azimuth antenna angle voltage by the elevation servo data appearing on elevation servo data =leads No."1 and No.2 The outputs of the two circuits areparalleled by using the common load plate resistor R 9315'for the gating tubes V-9303B and V9305A.' This is possibleudue to the fact that the gates formed by the :angle voltages and servo-voltages from the difierent an- 'tenna's do not overlap in time.

The "combined output thus developed is applied to terminals of the Servo Modulator Switch S-9301, which, depending upon the positionof the same, causes either an intensification or a-deintensification' of the range marks. :ln'the deintensifying position of switch 5-9301, the output of the switch is applied to :the grid of'the inverter tube "YV- 9304A. .The plate output of this tube is fed through -.the switch to the grid of the modulator tube V-9304B. "The output from the anode of' the modulator is a negative gate which is applied to the grid of mixer tube V-9313A.

' z-Inthe intensifying position of switch 8-9301, the inverter :tube 'V-9304A is shunted out of the circuit and the modu- -lating gates are applied directly to the grid of modulator tube V-9304B, its plate output-then in such case being cpositive and applied in similarmanner to the control :grid of tube V-9313A.

It ,is 1111118 observed that the range marks developed in range mark generator 18. and applied through the amplitude controlling =potentiometer146 and condenser 147 --are mixed on the grid of tube -V-931 3A with the; afore- :mentioned V-followerinformation in either' anadditive sorna-zsubtractivemanner. The voltage thus developed on wthe cathoderof the,mixer tube V.9313A is a measure of ixboth'the intensity of thevrangetmarks and the intensity cof 'theWfollower information, and is applied from the cathode of tube N-9313A through coupling condenser 3148" to the control grid of the mixer tubes- V-9319A, B. The =map generator23 (Figure '7) is identical with that one shown and claimed in the copending patent ,zzapplication of Green -et .al., Serial No. 222,511, filed April .23, l95 l,-andtassigned to the same assignee, and -:'serves to'develop two types of pulses, namely, cursor .pulses and L triggers. The cursor pulses are used in zr'su'ch-rpending application and herein to produce electr'onically and :visually the predetermined safe glidepath 149 :(Figurel) inthe elevation display and the runway course line 150 in'the azimuth display. The line 149 eorrespondsto the line-AB, andxthe linelfitl corresponds to the line CD, The L trigger is used insuch copending =applieation andherein fordisplay limiting or tailoring, "-as'well-tas for other purposes .herein. While the output -from the map generator 23 comprises cursor pulses and L -t'riggers, -'the input to 'themap generator comprises,

-on' the one hand the relatively slow varying azimuthelevation angle voltage and, on the other hand, the A1 system trigger. These cursor pulses developed -in the map generator-are applied to the mixer stage 22 in Figure 7, details of which are more clearly illustrated in Figures 3 and '8.

Cursor pulses from the map generator 23 in Figure 3 are delivered to the .grid of the cathode follower tube V-9314A, the cathode of which is in parallel with the' cathode of mixer tube V-9313A. The output from both of these cathodes is sent to the range mark mixer tubes f-$ 31913 and V-J319B.

The output of the mixer stage 22 (Figure 7) is applied to the composite video mixer 25, to which is likewise applied the radar video output from the video amplifier 24. The video amplifier stage 24 is now described in detail.

With reference to the following description of the video amplifier, it should be noted that the videoamplifier 24 is elfective as a passive network only during the duragrid of this tube is normally biased belowthe cut-off point of the tube by voltage from the voltage divider circuit which comprises in part resistances 151, "152. A gate is received from the fiip'-flop circuit comprising tubes V- 9329A and V-9329B. The startofthis gate; a video sampling gate, is coincident with the A1 trigger, and its trailing edge occurs approximately o-ne-quarterof a microsecond after the arival of the L trigger developed-inathe map generator. Crystal 154-establishes the level of the suppressor grid of tube V-9315 and the control grid of tube V-9316A at ground potential for the duration of this gate.

All video appearing on the grid of tube V-9315 is amplified and reproduced in theanode circuit duringthe time the video sampling gate 27 is present. During the gate interval the anode voltage of tube V-9315 drops, due to the higher current flowing at that time through the tube. This voltage drop is cancelled by theaction of the pedestal canceller tubes V-9316A and V9316B, which apply a positive gate of opposite polarity and of thesame amplitude to the output. The pedestal canceller circuit,

including tubes V-9316A, B, serves to'establish-a predetermined voltage level during the duration of the video sampling gate. The tube V-9317 amplifies the video signal and applies the same to the grids of the paralleled video mixer tubes V-9318A and V-9318B,-wvhich reproduce the video in their common cathode circuit. Crystals 155 and 156 serve as D. C. restorers. "The manner in which the video sampling gate 27 is obtained is described in detail hereinafter, it beingsufiicient for the present purposes to note that a sampled portion'of the radar video only has its effect on the control grids-of tubes V-9318A, B, which have their cathodes connected to the cathodes of similar mixing tubes V-9319A, B.

The other tubes V9320A,"B, having their cathodes connected to the cathodes of the aforementioned tubes V-9318A, B and 'V-9319A, B,-serve a a mixer forthe C and L triggers. Thus, range mark pulses, modulated servo data, i. e., V'-follower information, from the cathode mixer tube V-9313Aand mixed with cursor-pulses from the cathode oftube V-9314A are'applied to the paralleled grids of range mark mixer tubes V-9319A, B. These grids are maintained at a cut-off level until theappearance of a positive gate from the anode of gatingtube V-9314B, which is essentially the video sampling gate described above for purposes of changing the bias on the suppressor grid of tube V-9315. The range mark mixer stagetoperates only .for the duration of thisgate.

.C and L triggersafrom .theswitches of relayK-9302 are 7 tain amplitude during the time theelevati'on display is being developed, and suchpair oftriggers iscaused to applied to the controi grids of tubes i-9326A, B. The 7 winding of'relay 14-9302 isenergized onlyduring the azimuth scanning period; the relay gate developed by the switch 69shownin Figure Zbeing used for that purpose; 7

In other words, as will be more evident later, the C and L triggers, comprising a pairof triggers, have a cerhave a 'diflerentamplitude during the time the azimuth display is being developed, al lfor the purpose of develop i When the apparatus is intendedtoproducea display in proximity to the radar apparatusthe pairs of C and L: 7 triggers during both the'azimuthiand elevation scannmg periods may have the samc amplitude instead or different 7 video train now comprising the C trigger, the radar video, 7

range marksmodula ted in amplitude in accordance with 7 V-follower information, cursor pulses and L triggers, 1s,

include tubes V+9321A and 7B, V-dfiZZLA and B, V9323A' and B, and V--9324A and B. These four tubes have been 7 mentioned previously, 7 and serve in general to :feed the composite video train to the precision video amplifiers 7 Each 7 video out:

applied'to' four 's'eparatecathode follower stages which and to the precision remote line driver;

'putis' terminated with a 22-ohm resistance for protection 7 7 7 in case the external i 100-ohm :terminations are discord- 7 .nected. As mentioned previously, the video amplifier 24 157 7 operativeonly during the duration of the gate'27. The

manner in which this video gate '27 is developed and 7 applied to the video amplifieri 24, is now: describedin 7 7 'detail'.-' :Thsvideo gate, 2,7 ,is: formed in the stage 28 to which is applied theAl trigger. The stage 28, as shown 7 7 1 in Figures 3' and 8, includes a coincidence tube V 326, to the grid of which ,is, applied the Al'system trigger;

j The grid of this tube, in its quiescent state, is biased: 7 1 7 below cut-oft and is driven above cut-cit by the system 't rigger i A negative potential applied to the suppressor grid 7 of tube V-9326 maintains the tube bel'ow cut-off 7 until the arrival of the unblanking gates developed by operation of the antenna blanking switches 64 and 65 (Figure 2). The tube V9326 thus conducts only when the A1 trigger for the unblanking gate is simultaneously present on the control grid and suppressor grid of the tube V-9326. Thus, Al triggers appear in the anode circuit of tube 1-9326 only during the periods of the unblanking gates, and are applied therefrom to the flipflop circuit comprising tubes V-9329A, B.

The negative Al trigger causes tube V-9329B to cut off, and a resulting rise in its anode voltage is transferred through condenser 16% to the grid of tube V-9329A, which then starts to conduct. Tube V-9329A continues to conduct while tube V-9329B continues in its cut-oif condition until the arrival of a negative trigger on its control grid, i. e,, negative L trigger. The L trigger developed in the aforementioned map generator, delayed for approximately one-quarter of a microsecond in delay line Z-93tl2, is applied to the control grid of tube #93288 which, in its quiescent state, is normally cut ofi. This L trigger thus delayed appears as a negative trigger on the anode of tube V-9328B from Where it is applied to the control grid of tube V9329B. The video sampling gate 27 thus created is applied to the gating amplifier V-9315 to gate the incoming video and also to the control grid of gating tube V314B, for range mark mixing gating, and also to coincidence tube V-9327 for a C and L trigger gating. The gate starts earlier than the C trigger and terminates later than the L trigger in order to include both triggers within its duration.

It is noted that whereas the gate 27 applied to the suppressor grid of tube V-9315 is a positive gate, a gating voltage 27A of the same duration developed on the cathode of tube #932913 is applied to the control grid of tube V-9314B. The action and Purpose for applying pose.

time T {Figure ,12).

- such gating voltage to: the tube V-9327 will be more 7 7 7 evidentfrom the following description; 7 7 7 7 7 7 7 g In order toencompass both the C and Ltriggers on 7 :thecompositevidco, train, as alluded to previously, the 7 7 tubcsV-9327 and V,9325A' and B serve :a :useful m; 7, i

TheAl system trigger is applied through delay :line Z-9301 to the control grid of tube V-9325A. This 7 7 delay line imparts. a three quarters of a microsecond 7 delay to the systemtrigger, and it is observedthat the tube V-9325A; is a cathode follower mixer tube nor-7 7 mally maintained in its quiescent state at cut-off, The p delayed A1 trigger thus appearing n the cathode 0? tube :V-,-9,325A;is termed the C trigger and occursat The L trigger is applied to the i I I control grid of tube V-9325B which also, initsquiesccnt st ate, is maintained at cut-off. The L trigger appears 7 on the 7 common cathode of tubes V-i9325A and, B at, 7 7 7 somevariable T; (Figure 12) after the appearance ofthe r ss r- 7 771- 7 7 The precise time T1 is determined by the circuitryin 7 7 the map generator, and in general is a function ofthe azimuthorelevationantenna beam anglevoltageinav 77 7 cordance with the'principles and techniques described, and shown in the aforementioned patentapplication of Green et al., Serial No 222,511. triggersappearing on these commoncathodesaresapplied 7 7 to the control gridof the coincidence tube V-,-93Z7 which, i g in its quiescent state, is grid biasedbelow cutoff. The suppressor grid. of tube V-9327 isaisonormally biased, 7 7 7 iatavoltagebelowthe plate current cut off level of the tube Upon the arrival of the video sampling gate to the suppressor grid of tube V- 9327, the suppressor, grid 7 7 7 i is released from its cut-oir bias and the tube is enabled g to conduct for theduration of each C and L trigger ap lied to the control'grid ot tube;V-9327 7 7 7, 7 7 7 7 tube V-9327 are impressed on the primary winding .of 7 7 blocking oscillator transformer 7 T-93tl3. 7 Blocking oscillator .tube ,V-9328A: has applied to its grid the 7C and L 7 triggers, front the secondary 7 winding: of, 7 7

These triggers reproduced at the anode of transformer T-9303, and reproduces the triggers on its cathode. The grid of tube'V-9328A, in its quiescent state, is biased below the cut-off point, and this tube conducts only upon the application of the C and L triggers. The C and L triggers appearing on the cathode of tube V-932SA are applied to two parallel connected potcntiometers 165, 166. It is observed that the movable taps of these potentiometers 165, 166 are connected to opposite stationary terminals of the single pole double throw switch of relay K-9302, so that during the elevation scanning period the amplitude of the C and L triggers applied to the control grid of tube V-9320B is determined by the setting of the tap on potentiometer and conversely, the amplitude of the C and L triggers during the azimuth scanning period is determined by the setting of the tap on potentiometer 166. These controls 165, 166 are adjusted so that the C and L triggers each have an amplitude of l2-volts during the azimoth scanning period, and each have an amplitude of 20-volts during the elevation scanning period. To further complete the description of Figures 3 an 8, and to describe the manner in which the Az-El antenna beam angle voltage is transferred over a single conductor, reference is had to the relay control tube V-9308 and relay K-9301. The relay gate shown in Figure. 2 as being developed by operation of the switch 69 is applied to the control grid of tube V-9308. This voltage is in the order of 28 volts and serves to cause the tube V-9308, normally non-conducting, to conduct and to energize the winding of relay K93tl1.

It is noted that this relay gate brackets the azimuth antenna scanning period. Energization of relay K-9301 causes azimuth angle voltage to appear on the Az-El angle voltage lead 170 for use by other components of the system .11; is noted that the lead 170 thus carries Both the C and itamay beenergized in alike manner togive, as mentioned previously, the (land L triggers an amplitude of 12-volts during the azimuth scanning period and -volts during periods of elevation scanning.

Also considered; of importance in this present arrangement is the ISO-volt regulated power supply shown in 15 Figure-14. In Figure 14a regulated voltage of ISO-volts isobtainedusing a series regulator tube V9330 and control' tube V-9331. A '0-vol'tvoltage source has itsunground'ed positive terminal connected to the anode of tube V-9330 and to theanode of tube V9331 through 205 the series resistance 11-9457; The plate-cathode voltage drop of tube V -9330 establishes a positive voltage. of ISO-volts on the cathode of tube V9330 through the voltage: divider and amplifiercircui't comprisingqtube are connected to the unground'ed negative terminal of the 2-l0'-volt source. Any load changes causing voltage-variations on the ISO-voltoutput terminal 172' createsan opposing conductance condition in amplifiertube V'-9331. which, in turn, varies the. conductance level of tube V'-9330, thereby compensating for the load change;

Means and techniques forapplying compositavideo. train. bracketed by. C. alt-d112 triggers. to. cathodecll 0.) tubes 12.

niques-Whereby that portion of the composite videotrain. shown in Figure 11', which includes only the C' and I. triggers, and that portion of the video bracketed by the- C and- L triggers, are described above. It-is' only the is required for producing the cathode ray tube displays at a local station, and in that respect the C and L triggers either may be difierent amplitudes or the'same amplitude during the azimuth and elevation scanning periods.

The following descrip tion, in relationship to Figures 4 and 10, serves to fully describe'the manner in which, first, the video bracketed by the C and L triggers is applied as a negative going signal to the cathode 11 of the cathode ray tube 12, and, second, the manner; in which the gate channel connected to terminal No. 3' develops a positive going gating voltage for applicationto I the control grid 17 of tube 12, the boundariesof such gating voltage being determined by the C and-'L triggers, respectively. It is observed that the video channel connected to terminal No; 4; which includes the delay line 13 and amplifirsl'S and 16, is alluded to above. I

The videoamplifying-channel in general is conventional,, but of importance is the manner in which the final amplifier stage llh' is'controlled' in accordancewith certain triggers for purposes of preventing blooming at the extremities of the. cathode ray tube display. Such trigger. ing voltage is transferred'to the amplifier stage -16'throughtube V-6012A, which has its cathode connected to the cathode. of tube 16 as shown in Figure 10; The manner in which the. tube lti'is thus controlled.by'variati'ons of potential on' a cathode of tube V'-6.012A Will be more clear from the following description of the gate. channel which includes terminal No. 31. In' general this gate. channel, includingterminal No; 3, the blocking oscillator tube" V-6tlll5Z-ft, 13,. diode V-6007A, cathode follower V-6006A, multivibratorstage including tubes V-6006B';

trait'rto form the intensity gate and serves also to gate anag ams The operation of'this gate channel composite "video trainis applied to the-control grid ofthe first blocking; oscillator tube V-6tl05A, which serves'as the trigger tube; ResistanceR-Gtll'fi; which is serially connected with resist ance R -6tl1 '9; serves to determine the-intensity at whi.ch the blocking" oscillator tube-V-6005A- is triggered, and" this resistance' is adjusted so--that theblockingoscillator stage is fired by alIC'an-d E triggers, butrdoes not fire' on any video signals. It is' noted in this respect that the C and L triggers are always-of much greater. amplitude thanthevideo signals-- bracketed by *such' CY and L- triggers: I

It is-desired' to separate'theC' and IL triggers and lthis is accomplished as follows: consider the fact that any trigger which passes through, the gated cathode follower tubeV-titltlA i'sdelayed-"approximately 22' microseconds by the circuitryin thesweep; amplifier and is returned. 'as a-Dtri'gger. Themannerin which; the:C trigger is delayed" in-time-to form the- D trigger is' indicated in Figure 4 wherein the-delaymultivibrator 98 serves to impart such delay: The D trigger i's': applied'to the multivibrator.

V A stage comprising;tubes-'.V60'0,6B'and;V -6008A. The-.D. v assi: and resistor- R-9458, R"9459 and-"R-9460,wh1ch triggen initiates operation of this multivibrator stage. V 6006B; V 6008A', which, in turn, gates'oii the. cathode followertubeV-GSMA. Thus, while initially. the. C. triggercauses thegate'dcat-hode follower stage. V -60ll6A. to become conductive, the. subsequently developed D. trig-;-

ger-serves'toreturnthecathode follower. stage V-6006A.

to its normally non-conducting condition and. any, suh-I sequent trigger then is not' passed" through the: cathode follower stageV-GOOGA until after the. multivibratorstage I 4 V-6006B and V 6008A'isreturnedl'to.itshnormalcondis From the foregoing description themeans' and tech-- 7 tion.

A After the last mentioned multivihrator state. isv started, It" may be stopped by anysubsequent trigger. on. the. composite video train, i. e., by the L. trigger. This, is

c mplished. by applyingthe. blocking oscillator ulse specifically mentioned portion of the v1d'eotra1n that P developed in the. Winding, IZilfof the. blockingoscillator. transformerT-6003' through diode V60.07A.to thetanode. of tube, V6.006B.. Theintensity ofrthis pul'sefor. accomplishing this purpose may be adjustedby the. so-called. gated stop adjusting resistance171, which.is.s.erially con-.- nected with Winding g Y Recapitulating, the C trigger causestheblock. Qscilla tor' stage V'-6005A, Bto fire. The. resulting signal passes. through cathode follower V-600'6A. andiis delayed 3P5" proximately 22 microseconds by the delay in multivibra=- the order of 30 to l"4O.microsecond's, causes the. blocked;

oscillator stage V'-6tl05A, .B to fire.. The. blocked osciL- lator' signal'resulting from. this'l. trigger, fed to. theanode. of tube'V-6006B, causes the multivibratorstage V.-60.0.6.B,. V-6008A toreturn. to its normal. position. A negative. gate as a result is available at the cathode of. tube... V, -6008A, which is the same length. asthe. spacing, be=- tween the D and L triggers. After. this, negative. gate. is shaped. and'inverted by stage V-6ll08A, i't.is-coupl.ed.. tothe gridof the cathode ray tube, as anintensitying; gate. The intensity l'evelof this gate. is, set by adjusting. the' clipping; level of tube V'-6007B by the time.base.inten.- sity'control. Since the same trigger whichstops the in? tensity gate, i1 e.,,the,L trigger,,app ear-s in thevideo chan-. nel at several times normal; video. amplitu.de,,it-.is. desired. that some precaution betaken to prevent.blo.oming at the outline of the difierent azimuth, and. elevatinn dis? plays. This. is accomplished by applying. the. blocking; oscillator pulse appearing on.the: cathode offtube. \4-601'2A.

,to the cathode of the video. output. tube. (-6004,

stage 16.

It is noted, as previously described, that the composite video train in the. video channel is delayed by the delay line 13 a time in the order of A microsecond tothereby allow time for the blocking oscillator V6005A, V 6005B to fire and cut off tube V-6004 during the C and L trigger times. In this respect it is noted that the control grid of tube V-6012A is connected to the control grid of the blocking oscillator tube V-6005B.

. While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention. I

.' I claim:

. 1. In a system of the character described, a range mark generator for developing range marks, means for deriving voltages representative of the limits of scanning movement of a radiated antenna beam, means modulating said range marks in accordance with said voltages, means for deriving cursor pulses useful in establishing electronically a predetermined glide path, means for deriving pulses in timed relationship with the transmission'of energy by said antenna beam, gated mixing means controlled by said pulses for mixing said modulated range marks with said cursor pulses, means for deriving radarvideo, gated mixing means controlled by said pulses for mixing said radar video with said modulated range marks and cursor pulses, means deriving a pair of time spaced control triggers from each one of the aforementioned pulses, and means mixing said time spaced control triggers with said radar video, modulated range marks and cursor pulses so as to bracket the same.

2. The arrangement set forth in claim 1 in which a utilization device is provided, means deriving a gating voltage having a time duration commensurate with the spacing of said control pulses, and means rendering said utilization device effective to said video modulated range marks and cursor pulses only for the time duration of said gatingvoltage.

3. The arrangement set forth in claim 1 in which a pair of antennas are elfective alternately to produce said radiated antenna beam, and means for changing the amplitude of said control triggers in. a degree dependent upon which one of said pair of antennas is scanning so that the amplitude of said control pulses serves as an indication as to which of the two antennas is efiective at that particular time. I

4 In a system of the character described, means for.

developing pulses in timed relationship with the transmission of radiated energy in the form of an antenna beam; means for shifting the angular position of said antenna beam, means for deriving radar video signals from said radiated energy, cathode ray tube indicatingmeans including means for periodically developing cathpulse depending upon the angular position of the radiated antenna beam, a video channel coupling said video to an intensity control electrode of said cathode ray tube, said channel being normally inefiective in its quiescent state, to transfer video to said electrode, gate generating means for controlling the effectiveness of said channel, said gating means including means .for developing a gating voltage which starts substantially contemporaneously with said pulse and terminates a relatively short time interval after said control trigger voltage, means incorporating delay means for developing a second control trigger voltage which occurs an appreciable time after said pulse, a mixer stage for mixing said first and second trigger voltvoltages to said video channel, and means rendering said T coupling means effective in accordance with gating voltages applied thereto which starts prior to said second trigger voltage and ends after said first trigger voltage.

.5. In a system of the character described, a source.

of pulses for initiating radiated pulses and for receiving returning radar,video signals, a video channel normally inefifective to passsaid video signals, but rendered efiective upon application of a gating voltage thereto, said gating voltage starting substantially contemporaneously with each of said pulses and terminating after the expectant period of returning echo signals, and means deriving from each of said pulses a pair of control triggervoltages, means normally inefiective to couple said control trigger voltages to said video channel for transmission therethrough, and means rendering said coupling means effective upon application of said gating. voltage thereto.

6. In a system of the character described, a source of pulses for; producing radiated energy and resulting radar video echo signals, a video channel to which said video signals are applied, saidvideo channel being normally ineffective to pass said video signals, means derivingfrom each of said pulses a pair of time spaced control trigger voltages, the first of such trigger voltages occurring an appreciable time after a corresponding pulse and the other of said trigger voltages occurring at the termination of the expectant period of returning echo signals, means for developing a gating voltage having a time duration which starts substantially contemporaneously with each of said pulses and which ends an appreciable time after said second control trigger voltage, said video channel being controlled in accordance with said gating voltagento render said video channel effective, means. coupling said control trigger voltages to said video channel for transmission therethrough, said coupling means being normally ineffective but incorporating means whereby. the same is rendered effective upon application thereto of said gating voltage.

7. In an arrangement of the character described, a source of triggering pulses, a source of video signals produced in sequence in timed relationship with said triggeringipulses, a source of map limiting trigger voltages, means deriving from said triggering pulses and map limiting trigger voltages a gating voltage which has a time duration which begins substantially contemporaneously with said triggering pulses and which ends an appreciable time interval after said map limiting trigger voltage, a video channel coupled to said source of video signals but normally inefiective to pass said video signals, means applying said gating voltage to said video channel to render the same effective, means deriving from said triggering pulse a first trigger voltage which is delayed with respect to said triggering pulse, a mixer stage for combining said first and map limiting trigger voltages, a first and map limiting trigger voltage channel coupled to said mixer stage but normally ineffective to pass said first and map limiting trigger voltages, means applying said gating voltage to said first and second trigger voltage channel to render the same effective, and means coupling said first and map limiting trigger voltage channel to said video channel.

8. In an arrangement of the character described, a source of triggering pulses, a source of video signals, a source of map limiting triggers, means coupled to said source of triggering pulses for producing corresponding first delayed trigger voltages, a mixer stage for mixing said delayed. and map limiting trigger voltages, means coupled to said source of map limiting trigger voltages for developing a delayed map limiting trigger voltage, means for deriving from said triggering pulses and delayed map limiting trigger voltages a gating voltage which starts substantially contemporaneously with said triggering pulses and which terminate substantially contemporaneously with said delayed map limiting trigger, a first delayed and map limiting trigger voltage channel coupled to said mixer stage but normally ineffective to transfer the mixed first delayed and map limiting trigger voltages, means applying said gating voltage to said first delayed and map limiting trigger voltage channel for rendering the same effective, a video channel coupled to said source of video signals but normally ineffective to pass said signals, means applying said gating voltage to said video channel to render the same etfective, a range mark generator, a channel coupled to said range mark generator but normally ineifective to pass range mark signals, means coupling said gating voltage to said range mark channel to render the same effective and mixing means coupled to said video channel, first delayed and map limiting trigger voltage channel and range mark channel for producing a composite video output which includes the first delayed and map limiting trigger voltages, range marks, and video signals.

9. In an arrangement of the character described, a video channel, normally ineffective to pass video signals, means for developing a pair of time-spaced trigger voltages which bracket said video signals, a trigger voltage channel normally inefiective to pass said time-spaced trigger voltages, means deriving a gating voltage which starts an appreciable time interval before the first one of said time-spaced trigger voltages and which terminates a substantial time after the last one of said time-spaced trigger voltages, and means in each of said video and trigger voltage channels for rendering said channels effective upon application of said gating voltage thereto, and a mixer stage coupled to said video channel and trigger voltage channels for developing a composite video train which includes said time-spaced trigger voltages and video signals bracketed by said time-spaced trigger voltages.

10. The arrangement set forth in claim 9 including a range mark generator, a range mark channel coupled to said range mark generator but normally ineflective to pass range marks, said range mark channel incorporating 22 means for rendering the same effective upon application of said gating voltage thereto, and means mixing the output of said range mark generator with the output of said video channel and with the output of said trigger voltage channel.

11. In an arrangement of the character described, a video channel normally ineffective to pass video signals, means for developing a pair of time-spaced trigger voltages which bracket said video signals, a trigger voltage channel normally ineifective to pass said time spaced trigger voltages, means deriving a gating voltage which starts an appreciable time interval before the first one of said time-spaced trigger voltages and which terminates a substantial time after the last one of said time spaced trigger voltages, means in each of said video and trigger voltage channels for rendering said channels eilective upon application of said gating voltage thereto, a mixer stage coupled to said video channel and trigger voltage channel for developing a composite video train which includes said time spaced trigger voltages and video signals bracketed by said time spaced trigger voltages, a range mark generator, a range mark channel coupled to said range mark generator but normally ineffective to pass range marks, said range mark channel incorporating means for rendering the same efiective upon application of said gating voltage thereto, means mixing the output of said range mark generator with the output of said video channel and with the output of said trigger voltage channel, and means for modulating the intensity of the range marks generated by said range mark generator by voltages representing the limits of scan of an antenna causing said video signals.

References Cited in the file of this patent UNITED STATES PATENTS 2,483,644 Kelsey et a1 Oct. 4, 1949 2,513,962 Patterson July 4, 1950 2,585,855 Sherwin et a1 Feb. 12, 1952 

